This invention relates to methods for shipping, storing, and changing very large pneumatic tires typically for use with very large vehicles such as earthmoving vehicles, and more particularly to the methods enabled by the use of a removable tread belt pneumatic tire construction.
The tread belt pneumatic tires which are the subject of the method of the present invention are very large tires (greater than 120 inch outside diameter (OD)) generally designed for use on very large vehicles, generally off-the-road (OTR) vehicles such as earthmovers and large-capacity mining trucks (e.g., 300 short tons or more). These very large tires and vehicles are generally utilized at long-term mining or construction sites such as rock quarries, mines, foundries, major tunnel/roadway construction, dams/dikes, and the like. The very large vehicles are generally too large to transport to the work site normally, and are therefore often shipped in pieces to the work site where the pieces are assembled/welded together for use. As modern construction vehicles have evolved to larger and larger sizes, their tires have also grown to the point where conventional shipping of the tires becomes difficult. For example, an existing design of 360 ton (32,6530 kg) truck requires pneumatic tires of 150 to 154 inch diameter (3.91 meter) which is considered to be the maximum size tire reasonably possible to ship by conventional rail or roadway means in the United States. Tire weight is another consideration, as very large tires can weigh 8,000 pounds (3,628 kg) to 15,000 pounds (6,803 kg) or more per unmounted tire. The industry would like to progress to even larger, 400 ton (362,812 kg) or 450 ton (408,163 kg) trucks with correspondingly larger tires of 160 inch (4.07 meter) diameters or more. Depending on local limitations of shipping means (such as tunnel/bridge clearances and roadway weight limits), even somewhat smaller ones of the xe2x80x9cvery large tiresxe2x80x9d may pose significant problems, and may therefore require extraordinary transport means such as by helicopter.
Another problem faced by the users of very large pneumatic tires is changing the very large tires on the very large vehicles. The very large vehicles are generally employed in areas such as rock quarries, where the tires are subjected to high stress and loads, usually under harsh environmental conditions wherein tires are subjected to puncture-producing and wear-inducing conditions. Under these conditions, tires are damaged relatively frequently and must be changed at the work site. Even with removable-flange wheels, changing very large tires is a difficult and time-consuming process, requiring as much as 5 to 6 hours for a single tire change.
Another problem is storage of the very large tires at the work site. As tires become larger, more and more space is required for storage. Also, if operating conditions are particularly harsh, or if shipping of replacement tires xe2x80x9con demandxe2x80x9d is not practical, then increased numbers of spares must be stocked, further increasing the storage space needed. Furthermore, some job sites require different tread designs for different operating conditions. For example, wide treads with deep cleats may be needed for muddy conditions such as in rainy weather, versus normal-width treads with a different cleat design for operation on gravel or in dry weather conditions. Given the time consuming nature of the existing tire-changing methods, changing tires to obtain optimum tread patterns is not always feasible.
Finally, even if driving tires and steering tires on the very large vehicles are the same overall size, the tread patterns of the two types of tires need to be different for most effective operation. This again adds to the number of replacement tires which must be stored at a work site.
There is therefore a need for a method of shipping very large tires that allows for the employment of more conventional shipping means, and there is a desire to reduce the work site storage requirements as well as to improve the efficiency of the very large tire changing process.
Although tires having replaceable treads are known in automotive/motorcycle and conventional truck tire applications, it is not until recently that tread belt tires have been developed to meet the unique requirements of very large pneumatic tires for very large vehicles. U.S. patent application Ser. No. 09/424,089 entitled TIRE WITH IMPROVED REMOVEABLE TIRE TREAD BELT to Rayman, having a common assignee with the present invention, of which this invention is a continuation in part, discloses a tire with an improved removable tire tread belt for use on large earthmover vehicles. This tread belt tire (also called a xe2x80x9ctrack belt tirexe2x80x9d) xe2x80x9cis constructed of a removable tread belt assembly mounted to the outer circumferential surface of an inflatable tire carcass. A unique track belt design restrains the track from expanding while simultaneously improving the secure mounting of the track to the carcass and providing improved penetration protection. Also, the improved track belt will maintain a flatter tread profile which in turn will improve tread life and durability.xe2x80x9d
A predecessor version of removable treads or tracks for very large tires is discussed in U.S. Pat. No. 4,351,380, wherein certain prior art track belt tire assemblies comprise a plurality of ground-engaging xe2x80x9cshoesxe2x80x9d spaced about the periphery of the supporting structure. The heavy loads on the xe2x80x9cshoesxe2x80x9d result in great stresses being developed that sometimes lead to premature tire failure. The U.S. Pat. No. 4,351,380 is directed to an improved track belt assembly which comprises a plurality of shoes spaced about the periphery of a load-supporting structure and secured to a reinforcing belt structure disposed on the side of the shoe opposite the ground-engaging side thereof.
A body of prior art exists for tires with removable tread belts (see, for example, U.S. Pat. No. 3,897,814; U.S. Pat. No. 3,224,482; U.S. Pat. No. 3,087,526; and British Patent G.B. 2,073,109). However these patents were directed toward the addressing of various issues related to tires used by predominantly roadway vehicles such as automobiles and trucks. Examples of these issues include: varying cord spacing to reduce wear of the outer tread belt edge for xe2x80x9cenhanced service life and lower manufacturing costxe2x80x9d; improving transverse bending for xe2x80x9cbetter riding comfort and improved road holding abilityxe2x80x9d; and linking separate tread rings to improve xe2x80x9croad-holding capabilities and . . . silent riding.xe2x80x9d Accordingly, the prior art has varied the quantity, shape, placement and spacing of tread rings, reinforcing belts, inextensible cords, and interlocking grooves in the tire carcass and tread belt, but these variations have not been adequate to address the special needs of off-the-road vehicle tires, nor of very large tires in general.
There are still unsolved problems, relating to a pneumatic tire and tread belt assembly, concerning shipping, storage, inventory, and changing of very large tires on very large vehicles.
The present invention relates to an improved method for shipping, storing, and changing very large pneumatic tires which are used on very large vehicles such as earthmover vehicles. Very large tires of conventional construction are sometimes over 13 feet (4 meters) in height and approximately 8,000 pounds (3,628 K) to 15,000 pounds (6,803 K) in weight, and proposed very large truck designs require even larger tires. The size and weight of the very large conventional tires presents significant problems in shipping, storage and tire changing.
According to the invention, the very large tires are removable tread belt tires and the tread belt is shipped separately from the tire carcass. The removable tread belt is held in a compressed state for shipping, thereby having a significantly-reduced diameter for ease of shipping.
According to an aspect of the invention, a spacer is provided for the compressed tread belt forming the tread belt into an elongated straight-sided oval shape.
According to another aspect of the invention, the tire carcass may also be held in a compressed state for shipping.
According to the invention, removable tread belt tires are used to simplify and expedite the tire changing process for very large tires on very large vehicles, thereby producing time and cost savings, as well as making it feasible to change very large tire tread designs to accommodate different operating conditions. The inventive tire changing method includes the steps of (a) leaving the tire on the vehicle but partially deflating the carcass to make the tread belt loose; (b) laterally removing the tread belt; (c) laterally moving a replacement tread belt onto the tire carcass and properly positioning it; and (d) inflating the carcass to proper pressure to hold the replacement tread belt in place on the tire carcass.
According to an aspect of the invention, the steps (b) and (c) can be accomplished by driving out of the tread belt and by driving into the replacement tread belt, respectively.
According to an aspect of the invention, the steps (b) and (c) can be directly accomplished if the very large vehicle is first positioned with the tire to be changed elevated off the ground using, for example, a pneumatic jack, and then lowering the very large vehicle after completion of step (d).
According to an aspect of the invention, step (c) includes correct positioning of the tread belt on the carcass, e.g., appropriately positioning any interlocking lands and grooves so that the tread belt is positioned on the tire carcass as designed for normal operation of the assembled tire.
According to an aspect of the invention, a tread belt may be replaced with one of like tread design, or with one having a different tread design in order to accommodate different operating conditions such as different load-bearing surface conditions or different applications of the very large vehicles.
According to the invention, removable tread belt tires are used to reduce the physical size and inventory cost of storing replacement very large tires at a work site employing very large vehicles. A small number of multi-purpose tire carcasses are stored for use as replacements of damaged carcasses, and a larger number of tread belts are stored for use as replacements for the tread belts which are approximately four times more likely to be damaged or worn out compared to the carcasses.
According to an aspect of the invention, a variety of tread belt designs are stored at the work site, thereby enabling their use on the very large vehicles to accommodate a variety of operating conditions.
According to an aspect of the invention, at least some of the tread belts are stored in a compressed state, thereby further reducing storage space requirements.
Other objects, features and advantages of the invention will become apparent in light of the following description thereof.